Process for converting sodium sesquicarbonate to sodium monohydrate



March 19, 1935. R, B, MaC'MULLlN [g1-AL 1,994,892

PROCESS FOR CONVERTING SODIUM SESQUICARBONATE TO SODI'UM MONOHYDRATE-Filed July s, 1952 sheets-sheet 1 Egf- I' Egf- 7b leem/erf J/r fem for[on fai/2 ed Sodium qrbma fe and mmaf; l'a.. I

INVENTORS Faber* B. Ma CMU /r'n ATTORNEYS March 19, 1935 R. B. MacMuLLlNEr AL 1,994,892

PROCESS FOR CONVERTING SODIUM SESQUICARBONATE TO SODIUM MONOHYDRATEFiled July 6, 1932 2 Shee'bS-Sheei 2 Fly-...3-

42AM/.f Mz as Trona. la C/ Ammon/a (Enfers/0n 0 @vera han l A ATTO R NEYSv Patented Mar. 19, 1935 UNITED STAT-Esn 1,994,892 Pnoorss FonooNvEa'riNG QUICARBONATE v T DRATE f soDiUivr sE'ssoDIUM MoNoHr-` RobertB. MacMullin and'George Lewis Cunningham, Niagara Falls, N. Y.,Mathieson Alkali Works, Inc.,.New York, N. Y., a corporation of`Virginia Y assignors to The i n Appiiatio myc, 1932, jseriarivifcgibssi2 Claims;v (C1. ca -c3) This invention. relates to improvements in themanuiacture of sodium carbonate monohydrate, NazCOaI-IZO; Moreparticularly, the invention relates toimprovements inthe conversion ofsodium sesquicarbonate, NaI-ICO3-Na2CO3-2l-I2O, to

sodium carbonate monohydrate. Broadly, the invention comprises decarbonation-of an aqueous solution of sodiumr sesquicarbonate to anextent such that the molecular ratio CO2:Na of the solution is less than0.6 and thereafter precipitating sodium carbonate monohydrate from thesolution by the addition of ammonia in proportion less than thatprecipitating sodium carbamate,

NaNHzCOz. Specically, the invention includes,

in one aspect, decarbonation ofthe aqueous solu` tion of sodiumsesquicarbonate by precipitation of an insoluble carbonate and, inanother aspect, decarbonation of the aqueous solution of sodiumsesquicarbonate by .the addition of sodium hydroxide or a sodiumcarbonate lessvhighly car' bonated than sodium sesquicarbonate, sodiumcarbonate, NazCOaior example..A

In-an aqueoussolution of Aodium sesquicar bonate the ratio COzzNa is0.666.. We have found that the precipitation of sodium carbonatemonohydrateby the addition of lammonia to such solutions, in the generalmanner describedfin an application led March 25, 1932, Serial 'Number601,144 by Robert B. Mach/lullin, is much facilitated if the ratioC022Na is'rst reduced to a value less than 0.6. This reduction of theratio COzzNa can be accomplished in several Ways.

Carbon dioxide can be removed from the solution by precipitation as aninsoluble'carbonate, by the addition oi a soluble oxide or hydroxide ofa metal forming an insoluble carbonate, calcium oxide or calciumhydroxide, for example, the precipitated insoluble carbonate beingseparated from the solution, and sodium carbonate monohydrate thereafterprecipitated from the solution by appro-` priate addition of ammonia.Or, sodium hydrox? ide, NaOH, or sodium carbonate, Na2CO-3, can be addedto the solutionin amount suicient toreduce the ratio COzINa to a valueless than; Sodium carbonate monohydrate,` as Well as anhydrous sodiumcarbonate,ior example, can be used in this manner, and We havediscovered that much less sodium carbonatemonohydrate is required to beadded to bring'the ratio CO2:Na withinthis limit than is recovered,above what otherwise would be recovered, romthe modiiied solution. Theaqueous solutions of sodium sesquicarbonate in which the invention iscarried out may be free from sodium chloride or may contain sodiumchloride up to saturation. Y

' 59 parts of ammoniagas are The invention will be illustrated by thefollovvf 4 ing specific examples:

I. A solution of 73 .5 parts (by Weight) of sodium sesquicarbonate inabout180 parts of Water is treated with about 3 Vparts of calciumhydroxide. The temperature of treatment Temperatures of 2 0 60 C. aresatisfactory. The precipitated calcium carbonate is-separated Ainanyconvenientmannenby iiltratio-n for example, and sodium carbonatemonohydrate is then precipitated from the liquor by `the additionV ofam- Y monia While maintaining the ratio NI-IazNa in the range of about1: 1-3 1.

is unimportant;

Instead of dissolving the sodium sesquicarbonate in Water, as in theforegoing example, it may bedissolved `in anaqueous solution of sodiumchloride substantially saturated With respect to sodium chloride.V y

II. 28.5 parts of sodium carbonate monohydrate are added to a'solutionYof 39.8 parts of sodium sesquicarbonate m parts of Water, and aboutthen added to this mixture While maintaining a Vtemperature of 20-60"YC. About 46 partsrof sodium'carbonate monohydrate areprecipitated andseparated from the liquor. In a cyclic operation, 28.5 parts of thissodium carbonate monohydrate arere-used in the next cycle, gthe netrecovery being about 17.5 parts of lsodium vcarbonate monohydratepercycle. The liquor from which the sodium carbonate monohydrate hasbeenseparated can be subjected. to `any conventional recovery operations," fInstead otdssolvingthe sodium sesquicarbonate in Water, as in theforegoing examplait may be. dissolved inv lanzfaqueous solution ofsodium chloride substantially saturated with respect to sodium chloride.

III. 11 parts of sodium hydroxide are'added to a solutionof i vparts ofsodium sesquicarbonate and 58.5 parts Vof' sodium chloride in 183.5parts of Water, and about 40 parts of ammonia gas are then .addedjtothis mixture, While maintaining a temperature-oi 420"-,60" C. About 92parts of sodium carbonate monohydrate areprecipitated and separated fromthe liquor. Causticization ofr about l9%-of this recoveredsodium-carbonate monohydrate will yield the llparts of sodium hydroxiderequired for repetition of theY opera-r tion, leaving a net recovery ot75 parts of sodium carbonate monohydrate per cycle. .Theoperationillustrated by EXampleIII can be combined v`v vith carbonationand ,recovery operationsasypracticed in the conventional ammonia-soda.process in 'a' particularly advantageous manner as illustrated in thefollowing example:

IV. 22.6 parts of ammonia are stripped from the liquor from which thesodium carbonate monohydrate has been separated, in the operation ofExample III, by distillation, for example. The resulting ammoniacalbrine is then carbonated, as in the conventional ammonia-soda process,to precipitate 71 parts of sodium bicarbonate.

This precipitated sodium bicarbonate is 'sep-v tion. Fig. 1 furtherillustratesoperationsof thel typel illustrated by Example Fig-2 vfurtherillustratesoperations of the type illustrated by Example II. Fig. 3further illustrates operations ofthe type illustrated by the combined`operations of Examples II We claim: Y Y 1. In the conversion of sodiumsesquicarbonate to sodium carbonate monohydrate, the improvenient whichcomprises decarbonating an aqueous solution of sodium sesquicarbonate toan extent such that the ratio C022Na of the solution is less than 0.6and thereafter precipitating sodium carbonate monohydrate from thesolution bythe addition of ammonia in proportion'less than thatprecipitating sodium carbamate.

2. In the conversion Vof sodium sesquicarbon- 'and IV.`

Yate to sodium carbonate monohydrateythe improvement which comprisesadding an oxide of ametal forming an insoluble carbonate to an aqueoussolution of sodium-'sesquicarbonate to precipitate carbon dioxide as aninsoluble rcarbonate until the ratio COzzNa of the solution is less than0.6,.removingfof the insoluble carbonate and thereafter' precipitatingsodium -carbonate monohydrate from the solutionfby the addition ofammonia in proportion less than'that precipitating sodium carbamate.

' V3. In the conversion of sodiumgsesquicarbonate to sodium carbonatemonohydrate, the improvementwhich comprisesadding sodium hydroxide to anaqueous solution of sodium sesquicarbonate until the ratio CO:Na ofthe's'olution isfless than 0.6 and thereafter precipitating sodiumcarbonate monohydrate from the's'olution by the laddition of ammonia inproportion lessthanthat precipitating sodium carbamate.v

4. In the conversion of vsodium sesquicarbonate to sodium carbonatemonohydrate, the improvement which comprises adding an oxide of a metalforming an insoluble carbonate to an Y aqueous solution of sodiumsesquicarbonate-also containing sodium chloride to precipitate carbondioxide as an insoluble carbonate until the ratio COzrNa of the solutionis less than 0.6, removing the insoluble carbonate and thereafterprecipitating sodium carbonate Ymonohydrate from the solution by theaddition' of ammonia vin proportion less than thatV precipitating sodiumcarbamate. Y

5. In theconversion of sodiumsesquicarbonate to `sodium carbonatemonohydrate, the improvement whichV comprises addingfsodium hydroxide toan aqueous solution of sodium sesqui'carbonate Vcarbon dioxide as an`ing sodium carbamate. v

also containing sodium chloride until the ratio COzrNa of the solutionis less than 0.6 and thereafter precipitating sodium carbonatemonohydrate from the solution by the addition of ammonia in proportionless than that precipitating sodium carbamate.

6. In the conversion of sodium'sesquicarbonate `to'sodiumcarbonatemonohydrate, the improvement which comprises adding sodiumcarbonate monohydrateto an aqueoussolution of sodium sesquicarbonateVuntil the ratio CO2:Na of the solution is less than 0.6 and thereafterprecipitating sodium` carbonate monohydrate from the solution by. theadditin of ammonia in proportion less than that precipitating sodiumcarbamate.

y l 'L Irrthe conversion of sodium sesquicar- Vbicar- 0nate"'to"sodiumVcarbonate monohydrate, the improvement which comprises adding a base ofa metal forming an insoluble carbonate to an aqueous solution-'of sodiumsesquicarbonate to precipitate carbon dioxide as an insoluble carbonateuntil vthe ratio COzNa Voi the solution less than 0.6,"removingthe-insoluble carbonate and thereafterl precipitating sodium carbonatemonohydrate' from the .solution by the addition of ammonia in proportionless than that precipitating Vsodium Vcarbamate. I

8. In the Aconversion of sodium sesquicarbon-V ate v.to sodiumcarbonatemonohydrate, the improvement which comprises adding anhydroxide of a metal forming ari-insoluble carbonate to an aqueoussolution of sodium sesquicarbonate to precipitate carbonV dioxide as aninsoluble carbonate until the ratio COzfNa of the solution is less than0.6,-removing' the insoluble carbonate and 'thereafter precipitatingysodium carbonate monohydrate from the solution by the addition ofammonia in proportion less than that precipitating sodiumcarbamate.

. 9. In theconversion of sodium sesquicarbonate to sodium carbonatemonohydrate, the improvement vWhiclicomprises adding a base of a metalforming an insoluble carbonate to an `aqueous solution of sodiumsesquicarbonate also containing sodium chloride to precipitatecarbondioxide as .an insolublecarbonate until the ratio CO2-:Na of thesolution is less than 0.6, removing the insoluble carbonate-andthereafter precipitating sodiumcarbonate monohydrate from the solutionby the addition of ammonia in' proportion less than that precipitatingsodium carbamate; l Y Y 1I l0.V In the conversion of sodiumsesquicarbonate to sodium carbonate monohydrate, the immovement-Whichcomprises adding an hydroxide of-a metal'forming an insoluble carbonateto an aqueous Vsolution of sodium sesquicarbonate also containing-sodium Vchloride 'to precipitate insoluble carbonate until the ratioCO2:Na of the solutionV is less than 0.6, vremoving the insolublecarbonate and thereafter precipitating sodium'carbonate monohydrate fromthe solution by theaddition of 'ammonia inproportion less than thatprecipitat- 1l. In the conversion of sodium sesquicarbonate tosodiumcarbonate monohydrate, the improvement Which comprises adding a sodiumcarbonate less 'highly carbonated than sodium sesquicarbonate toanaqueous solution of sodium sesquicarbonate `until' the ratio CO2:Na ofthe solution is less than 0.6and thereafter precipitating sodium.carbonate monohydrate from` the solution by the Yaddition of ammonia in.proportion Iess than that precipitating sodium carbamate.

12. In the conversion of sodium sesquicarbonate to sodium carbonatemonohydrate, the im-A until the ratio COzzNa of the solution is lessthan 0.6 and thereafter precipitating sodium carbonate monohydrate fromthe solution by the addition of ammonia in proportion less than thatprecipitating sodium carbamate.

ROBERT Bg MACMULLJN. GEORGE LEWIS CUNNINGHAM.

